Outlet testers have been used to detect whether the wiring to a 120 volt outlet is correctly installed. An outlet may also be referred to as a receptacle or a socket. A properly designed 120 volt outlet includes a live or hot terminal, a neutral terminal, and a ground terminal. Typical 120 volt outlet testers include a lamp and a resistor connected in series between the live terminal and the neutral terminal, the live terminal and the ground terminal, and the neutral terminal and the ground terminal. The 120 volt outlet testers are typically exposed to approximately 15 amps of current and the lamps and resistors in the tester are selected accordingly.
If the 120 volt outlet is wired correctly, the circuit between each of the terminals will be completed causing the lamps to illuminate. However, if the 120 volt outlet is improperly wired, a leg of the circuit will not be completed causing at least one of the lamps to remain unlit. The wiring problem may be identified based on which lamps do not illuminate after the 120 volt outlet tester has been placed in the outlet. By testing the wiring to the 120 volt outlet prior to plugging an electronic device into the outlet, damage to the electronic device caused by improper wiring may be avoided.
Some electronic devices, such as clothes dryers and electric ranges, are plugged into 240 volt outlets. A three prong 240 volt electric outlet includes two live or hot terminals and a neutral terminal. A four prong 240 volt electric outlet includes two live or hot terminals, a neutral terminal, and a ground terminal. The 240 volt circuits are typically 30 amp circuits for dryers or 50 amp circuits for electric ranges. Thus, a 240 volt outlet tester would be exposed to current levels two to three times higher than a 120 volt outlet tester. A circuit designed for use within a 120 volt outlet tester would be severely damaged if used in a 240 volt outlet application. Because of the differences in terminal design, plug design, and the amount of current and voltage supplied at the outlet, a 240 volt outlet cannot be tested using an outlet tester designed for a 120 volt outlet.
An improperly wired 240 volt outlet is a safety hazard and may cause damage to a clothes dryer, an electric range, or other electronic device that is plugged into the improperly wired 240 volt outlet. Additionally, some wiring errors may cause an electronic device chassis to become “hot,” which may electrocute a person contacting the chassis causing severe injury or even death. Accordingly, there needs to be a way to test 240 volt outlets prior to plugging a device into the 240 volt outlet.